Among flat-panel display devices, liquid crystal display panels (LCD panel), having the advantages of low thickness, light weight, low power consumption and low electromagnetic emission, are widely used in information devices such as cell phones, computers, televisions, personal digital assistant, etc.
Residual image is one of the obvious defects of the existing LCD panels. If a LCD panel displays a same frame for a long time, when the frame is switched to a next one, an image of said frame will remain faintly on the screen. This faint image is referred to as a residual image. The reason is that the polar particles in the LCD panel can move toward the upper substrate and the lower substrate of the LCD panel along a direction of the electric field, and gather at the surfaces of the upper substrate and the lower substrate, thus generating a DC residual voltage. When the density of the gathered polar particles reaches to such a degree that the DC residual voltage generated can affect the deflection angle of the liquid crystal molecules in the liquid crystal cell, the LCD panel will display images distortedly. Therefore, when the frame is switched to a next one, the gathered polar particles will remain at the surfaces of the substrates, and retain the original image, thereby leading to a residual image.
In the existing technologies, the defect of residual images of LCD panels can be overcome by optimizing the processing environment and conditions so as to reduce the content of impurities in the LCD panel, by optimizing the selection of materials, for example, selecting less pollutive encapsulating materials, steady liquid crystal materials containing less polar particles, or appropriate alignment film, so as to reduce the content of polar particles in the LCD panel, or by adjusting gamma voltage so as to reduce the difference among common electrode signals at different locations in the LCD panel, then reduce the difference of common electrode signals with different gray scales, and finally find out a most appropriate monochrome voltage to overcome the defect of residual images.
The inventor found that the methods of overcoming the defect of residual images in the existing technologies are limited by factors such as materials, processing, and manual error, and therefore cannot effectively overcome the defect of residual images.